Circuit interrupter



April l, 1941. 1 SANDIN Er AL 2,236,580

CIRCUIT INTERRUPTER Filed Dec. s1, 1957 2 sheets-sheet 1 24 2a /lo /4 /6 /a 3o 20 604750 wl r/ (0.4 T50 w/rH 60k/c 76/0 5019/6 46/0 WITNESSES: NVENTRS c, jerome anc/ff and WM gf/' April l, 1941.

wnNssses;

J. sANDlN TAL 2,236,580

CIRCUIT INTERRUPTER Filed Dec. 3l, 1937 2 Sheets-Sheet 2 IN V EN TO R 5 faro/n e ana/fn and @Wa/7 .5. pay/ which is shown, for receiving the respective poles of the interrupting structure. Each pole oi' the ci-rcuit interrupter comprises a xed contact I4 and a movable contact I8 yieldingly supported upon the end of a contact arm I8 mounted for swinging movement about shaft 20. The fixed contact I4 is connected by a conductor 22 to a connector 24. The .connector 24 is provided with a threaded stud 26 for clamping one of the line terminals 28 thereto. The movable Contact I8 is connected by a flexible conductor 38 -to a suitable electro-responsive device, not shown, i'or tripping the pole unit mounted in the com-partment I2. The electrical circuit from the electroresp-onsive .tripping device terminates at .the other line terminal 32 of the interrupter.

The movable contact arms I8 are preferably n Vinsulatingly"secured to atie bar-34 which coin one end thereof as shown in Fig. 5. As shown more clearly in Figs. 2, 3-and 4, the plates 40 are more closely spaced at their slotted ends and are arranged with their slots in superimposed relation so as to form an aligned groove. Inasmuch as the plates 40 .converge towards their slotted ends, someof the plates are somewhat shorter than the others in order to maintain suilicient spacing between .the ends of the plates to prevent insulation failure. The'wall members 38 are held in clamping engagement with the plates 40 by means of rivets 42 passing transversely therethrough so-a-s to unite the plates and wall members in a unitary structure.

The wall members 38 are also provided with indentations or recesses extending from the outer surface inwardly at 44 so as to provide an intermediate shoulder portion 46 having a vertical bore 48 therethrough fo-r receiving a suitable mounting screw 50. The mounting screw 50 is adapted to be screwed into -the base l0 thereby securely holding the arc extinguishing structure in proper relation with respect to the contacts I4 and I6.

The arc extinguishing plates 40 are preferably o-f magnetic material such as iron so that when the arc is drawn between the contacts I4 and I6 as a resul-t of movement of the contacts I6 'through the groove 'formed by the slots. in the plates 40, t'he magnetic reaction set up by the plates 48 will move the arc towards the apex of the slots and into the plates. The plates 40 thus split the arc into a plurality of short serially related arcs and extinguish the same by dei-onizing the are stream in a, manner which is well known in the art. In order to prevent extremely heavy ourrent arcs which travel with relatively high velocitie-s, due to the magnetic actions set up in the plates, from moving beyond .the ends of the plates 40 and restriking into a single arc, two transversely disposed barriers 52 are provided between the Wall members 38.as more clearly shown in Figs. 2 and 3. Thebarriers 52 are disposed at medial points ailong'the arc path, so that in the event the short arcs succeed in passing through the plates and tend to restrike as a single arc Amembers are immersed in a along mey outer edges of the plates, there wm be I a sudden lengthening of the arc at fthe barriers 52, causing the are to be extinguished.

The opposed surfaces of the side wall members 4 38 adjacent the arc receiving slots ln the' plates 40 taper inwardly in the direction of arc movement so as to provide a convergent entrance passage for the arc. The narrow constricted portion between the opposed wall members 38 extends a considerable distance ailong the arc receiving slots and again .widens in the direction of arc movement, as more clearly shown in Fig. 1. The tapering entrance portion as provided by the side walls 38 serves to contract the arc so as to meditate entry of the am into the plates lo. 'The inwardly projecting portions of the'side walls 38 also nserve torimbed the metallic-portiamo! the Thisplates 40 adjacent the sides of the slots. construction lessens the tendency of the arc to strike to an intermediate plate along the side edges of the slot prior to movement of the movable contact I=6 to its full open position. Also if an arc were at a point along the side edges ofthe slot, f-urther arc movement would likely be prevented and failure of the structure would result.

Even though the edges of the plates adjacent the slot are not directly exposed to .the arc, there is a :tendency for the arc to-move laterally from side to side of the slot, -thus causing rapid deterioration of the side walls of the members 38. The members 38 are preferably formed of a cold molded material constituting 22% hydrated lime, 38% powdered silicate and 40% asbestos nbre. Although this substance has excellent heat resisting properties and is a good insulator, the repeated action ,of ain arc playing upon the side walls defining the arc passage causes the side walls to blister and eventually causes a material lowering of resistance. In order to prevent the deleterious effect iof the arc upon the side wall members, we impregnate the wall members with a substance which produces a gas when acted upon by an arc, so as .to repel the arc and maintain it centrally of the passage during its movement into the plates 40.

Although the cold molded material above described is preferred, other cold mol-ded materials may be used, such as a composition comprising 50% Portland cement and 50% asbestos fiber or a composition comprising 50% Portland cement, 15% baryltes and 35% asbestos fiber. Horn fiber is also suitable as a material from which the wail members 38 may be constructed. A porous refractory material comprising 30% talc, 2% feldspar and 68% clays is al-so suitable but less desirable than 'the cold molded materials since it is more brittle and less capable of withstanding shock. I

The fibrous composition from which the wall members 38 are composed is preferably impregnated inthe following manne Prior to assembly of the wiall members with .the plates 40, the saturated solution of boric acid and allowed to remain in that soiution for a time suflcient to enable .the members to .absorb a considerable quantity of the solution. The members are then removed and dried at a temperature below that at which boric acid decomposes for a period of time suillcient to remove substantially all moisture. If necessary, additional impregnating treatment-s 'as above described may .be employed to increase the amount of |boric acid deposited in the voids of the members. We have .found that for the particular permitted .to impinge on the plates accesso solution of boric acid for at least 30 minutes,- followed by a drying period of about four hours at a temperature of 120 C.' is suiiicient to impregnate the members. The boric acid particles with which .the side wail members 88 are impregnated are schematically illustrated at 53 in Fig. 4.

Thed use oi boric acid in the solid form as a liner for arc passages in expulsive circuit interrupters is well known. We have discovered` that solid boric acid as aliner of the side walls of the entrance passage of an arc extinguisher of the:

type herein disclosed is undesirable inthat it proupon the conducting member.

duces such a turbulent blast of gas in the entrance passage so as to interfere with the arc movement into the deionizing plates. By impregnating the side walls of the arc passage with boric acid just suilicient gas is liberated, which is directed against the arc stream in the presence of the arc, to maintain the arc out of contact with the walls, The presence of the water vapor resulting from the action of the arc upon the boric acid does not in-v terfere with arc movement by the magnetic reaction set up by the magnetic plates and is further beneficial in that it assists in deionizing the arc stream. Although we prefer to impregnate the insulating wall members 38 with a solution oi boric acid, other materials such as gypsum may be used, but with somewhat inferior results; Both gypsum and ammonium alum produce libat G8, interposed therebetween. It is desirable to confine the use of boric acid mainly to the portions of the plates B0 and 62 adjacent each side of the V-shaped slot. The presence of boric acid immediately adjacent the closed end of the slot may cause the generation of sumcient gas to prevent the movement of the arc into the plates @t and 62. The presence of the thin layer of boric acid 84 along the side edges of the slot performs the same function as the boric acid impregnated in the side walls 38 of the arc extinguishing structure. That is, a small quantity of water vapor is released by the action of the arc and directed against the arc so as to maintain the arc centrally positioned as it moves into the delonizing plates of the arc extinguishing structure.

'I'he further embodiment of our invention is shown inl Fig. '7 in which the numeral 10 desigcuit interrupter. 'I'he upper end of the tube 10 is provided with a metallic ferrule 12 which is threaded for the reception of a cap 16 which serves to hold a button 16 of a fuse link 18 in engagement with the ferrule. The cap 14 also securely seals the upper end of the tube 10. The lower end of the fus link 18 .is provided with a ilexible conductor 80, the end of which extends through the open end of the tube 10 and is secured to a metallic ferrule 82 by means of a thumb screw 84. Tube 1B of iibrous material is preferably impregnated with a saturated solution of boric acid, the

, boric acid being indicated at 86. Thus when the eral quantities of water vapor when acted upon by an arc but are less desirable than boric acid since they have a relatively low resistance when in the molten state. Boric acid on the other hand, retains its insulating properties even when it is in the liquid state and for this reason it is preferred as the impregnating substance.

As shown in Figs. 1 and 2, a barrier 5 of ibrous material is inserted between the end of the arc extinguishing structure and the conductor 22 and connector 24. The barrier 54 is also preferably treated with boric acid solution so that in the event an arc should lmplnge thereupon a gas will be liberated which repels the arc and also assists in its extinction. The presence of boric acid in the barrier member is shown at 55 inFig. 2. We have also discovered that the metallic conducting parts of the breaker such as the movable contact arm I8, conductor 22, connector 24, screws 26 and terminal members 28 and 32 may be coated with boric acid as by dipping these parts in a saturated solution of boric acid or by spraying the saturated solution of boric acid thereon. The metallic surface of these members retains a suilicient quantity of boric acid, so that when an arc tends to strike thereto the boric acid will be decomposed surrounding the metallic conductor with a blast of water vapor which repels the arc and prevents the formation of an arc terminal In this manner the conducting members are protected from decomposition by the arc in the event that an arc should accidentally strike thereto. j

In F'igs. 5 and 6, a modied form of plate structure is shown which may be employed with side wall members 38 in the arc extinguisher previously described, Instead of using a single plate of'magnetic material having considerable thick. ness, two thinner plates 80 and 62 are employed having a thin layer of solid boric acid indicated arc is established within the tube 18 as a result of blowing of the fuse link 18, it decomposes a portion of the tube 1t, creating a deionizing blast of gas which extinguishes the arc with an expulsive action. The presence of the boric acid within the walls of the tube 10 increases the gas generated and hastens the arc extinguishing process, thereby materially decreasing the deteriorating effect less desirable for this particular purpose than boric acid.

Although we have shown and described specic materials and structures for the purpose of carrying out our invention, it shall be understood that the same is for the purpose of illustration, and that other materials than those named could be used for coating metallic members or for impregnating porous insulating materials to achieve the objects sought in this invention, and that we do not wish to be limited by said illustrations except as specifically set forth in the appended claims.

We claim as our invention:

l. In a circuit interrupter, an arc chute comprising a pair of spaced wall members of porous inorganic insulating material, said wall members having a portion of their opposed surfacesv adjacent one end tapering towards each other to provide a converging entrance passage, a. plurality of spaced metallic plates disposed betwee' said wall members, and means for moving ai arc from said entrance passage into said plates, said wall members being impregnated with a solution of a materialwhich gives oi a gas when actedupon by an arc to provide a iiow of gas against the arc to maintain it centrally of said wall members as it moves into said plates.

2. In a circuit interrupter, an arc chute comprising a pair'of spaced wall members of refractory insulating material, said wall members having a portion of their opposed surfaces adjacent one end tapering towards each other to provide a converging entrance passage, a plurality of spaced metallic plates disposed between said wall members, said plates being composed of a ferrous material and having a V-shaped slot in one end thereof, portions of said plates adjacent their slots being completely recessed in said tapering portions of said wall members, and means for establishing an arc in said entrance passage, said arc being moved towards the closed end of said slots and into said plates by the magnetic reaction set up thereby, said wall Vmembers being impregnated with a solution of material which gives on' a gas when acted upon by an' arc to provide a flow of gas against the arc to maintain it centrally of said wall members as it moves into said plates.

3. In a circuit interrupter, means for opening the circuit to establish an arc, an arc extinguishing device in which said arc is established, said arc extinguishing device comprising a plurality of plates ofmagnetic material, said plates having a v-shaped slot in one end thereof, said arc being moved into said plates by the magnetic reaction set 'up by said plates, a pair of unitary side wall members of cold molded insulating material impregnated with a solution of boric acid, said wail members having ,spaced longitudinally extending grooves for receiving the side edges of said plates, and means for holding said side wall members in clamping engagement with said plates, said boric acid emitting a blast of water vapor when said arc impinges upon said side wall members which blast of vapor maintains the arc centrally positioned with respect to said wall members and aids in extinguishing the arc.

4. An arc extinguishing device for circuitl interrupters comprising a plurality of pairs of plates of conducting material, said plates having a V-shaped arc receiving slot in one end thereof, a thin'layer of material which gives oi! a gas when acted upon by an arc disposed in contiguous relation between each pairof plates at least between the greater portion of said plates adjacent the sides of said slots, and means for supporting said pairs of plates in spaced relation with respect to each other.

5. An arcchute for circuit interrupters comprising a pair of wall members of insulating material, a plurality of plates of conducting material disposed in spaced relation between said .wall members, said plates having an arc receivof said slots for causing a blast of gas againstA an arc playing in said slots to maintain the arc positioned centrally of said slots.

8.. An arc chute for circuit interrupters comprising a pair-...of wall members of insulating material, a plurality of plates of conductingI material disposed in spaced relation between said wall members, said plates having an arc receiving slot in one end thereof, some of said assenso plates being spaced more closely than `others, and a thin layer of boric acid between said more f closely spaced plates at least along the greater plortsion of said plates adjacent the sides of said '1. An arc extinguishing device for circuit interrupters comprising means of insulating material defining two opposed surfaces of an arc passage, said means of insulating material having a plurality of spaced grooves disposed along saidopposed surfaces, a plurality of plates of conducting material disposed transversely between said opposed surfaces and having their side edges supported within saidK grooves. each of said p1ates\l having an arc receiving slot in one end thereof, a plurality of said plates having a part of'their slot defining portions completely recessed in said means of insulating material to lprevent an arc established adjacent said recessed portions from striking thereto, at least the 0pposed surfaces of said insulating material delining said arc passage being impregnated with `a material which gives oif a gas when acted upon by an arc to4 repel the arc for preventing sustained intimate contact of the.arc with said insulating material.

8. In an arc extinguishing device for circuit interrupters comprising a pair of spaced wall members of insulating material, said wall mem. bers having a portion of their opposed surfaces adjacent one end tapering towards each other to provide a converging arc receiving passage, a plurality of spaced metallic plates disposed between said wall members, said plates having a V-shaped slot in one end thereof and considerable portions thereof defining the sides of said slots completely embedded in said tapering portions of said wall members for preventing an arc from striking to said embedded portions, at least the opposed surfaces of said wall members being impregnated with a material which gives of! a gas when acted' upon by an are to repel the arc for preventing sustained' intimate contact 'of the arc with at least said tapering potions of. said wall members.

In an arc extinguishing device for circuit interrupters comprising a pair of spaced wall members of insulating material, said wall members having a portion of their opposed surfaces adjacent one end tapering towards each other to provide a converging arc receivingy passage.'

a plurality of spaced metallic plates disposed tween said wail members, said plates havingbea V-shaped slot in one end thereof and considerable portions thereof defining the sides of said slots completely embedded in said tapering portions of said wall members for preventing an arc from striking to said embedded portions, atleast vthe opposed surfaces of said wall members being impregnated with a solution of boric aci vide a flow of gas towards the arc when;l ttlepagc impinges against said wall members to prevent sustained intimate contact of the arc with said 1 arc extinguishing device com glurality of plates of conducting matlze'uli'ai;mio:I

l an arc, ,a pair of wall m disposed on opposite sides of said plates su :11: ducting material for holding said plates in spaced relation with respect to each other and for guiding the arc into said plates, said wall members being composed of cold moldedmaterial including asbestos fibre and an inorganic binder and .being impregnated with a material which gives off gas when acted upon by an arc for preventing the are from maintaining sustained intimate contact with said wall members.

1l. An arc extinguishing device comprising a plurality of plates *.onducting material for extinguishing an arc, a pair of wall members disposed on opposite sides of said plates of conducting material for holding said plates in spaced relation with respect to each other and for guiding the arc into said plates, said wall members being composed of cold molded material including asbestos bre, hydrated lime and powdered silicate and being impregnated with a material which gives ofi gas when acted upon by an arc for keeping the arc out of sustained intimate contact with said wall members.

12. An arc extinguishing device comprising a plurality of plates of conducting material for extinguishing an arc, a pair of wall members disposed on opposite sides of said plates of conducting material for holding said plates in spaced relation with respect -to each other and for guiding the arc into said plates, said wall members being composed of cold molded material including 40% asbestos bre, 38% powdered silicate and 22% hydrated lime and being impregnated with a solution of boric acid to provide a iiow of gas towards the arc when the arc impinges against said wall members to prevent Athe arc from making sustained intimate contact with said wall members.

13. An arc extinguishing device comprising a plurality of plates oi conducting material for extinguishing an arc, a pair oi wall members disposed on opposite sides of said plates of conducting material for holding said'plates in spaced relation with respect to each other and for guiding the arc into saidplates, said wall members being composed of cold molded material including asbestos bre and Portland cement and being impregnated with a material which gives oil gas when acted upon by an arc for keeping the arc from making sustained intimate contact with said wall members.

14. An arc extinguishing device comprising a plurality of plates oi conducting material'for extinguishing an arc, a pair of wall members disposed on opposite sides of said plates of conducting material for holding said plates .in spaced relation with respect to each other and for guiding the arc into said plates, said wall members being composed of cold molded material including 50% asbestos ilbre and 50% Portland cement and being impregnated with a solution ot boric acid to provide a dow of gas towards the arc when the arc impinges against said wall members to prevent the arc from making sustained intimate contact with said wall members.

l5. An arc extinguishingdevice comprising a plurality of plates of .conducting material for extinguishing an arc, pair of wall members disposed on opposite sides of said plates of conducting material for holding said plates in spaced relation with respect to eachother and for guiding the arc into said plates. said wall members being composed of cold molded material including asbestos libre, Portland cement and barytes and being impregnated 1with a materialwhich gives oil gas when acted upon by an are for keeping the arc out of sustained intimate contact with said wall members.

16. An arc extinguishing device comprising a plurality of plates oft conducting material for repelling the are when .the arc impinges against 

